During use, the alkaline cleaning solution can show some reaction with carbonates out of the air or caused by soil to lớn remove. This is especially relevant (but not limited to) for brewery and beverage plants because of the higher amount of CO2 in the atmosphere. If there is an expected impact of the caustic by carbonic acid or if the cleaning solution is used over a long period of time it’s needed to lớn take the level of carbonization into tài khoản for determining the exact concentration. This is because the cleaning activity of sodium carbonate (Na2CO3) is strongly reduced but the titration simulates a high concentration of the active cleaner (NaOH).

Necessary chemicals:

- Hydrochloric acid with suitable normality (in most cases 0.5N)

- Phenolphthalein (1.0% solution)

- Methyl orange (0.1% aqueous solution)

Method:

- Pipette the suggested quantity of the test solution into a flask (when not described differently: 50 mL)

- Add 2-5 drops of the Phenolphthalein-solution

- Titrate up to lớn color change of the indicator from red to lớn colorless

- The consumption in mL is the P-value

- Add 3-5 drops of the Methyl orange- solution

- Titrate without refill/reset the burette up to lớn color change from yellow to lớn orange/red

- The consumption (total consumption including the first titration) in mL is the M-value

Calculation:

The sodium hydroxide concentration (NaOH) can be calculated as follows:

(Titrate of 50 ml application solution with 0.5N hydrochloric acid)

- (2P-M) x 0.04 = concentration of NaOH in % (by weight)

The concentration of soda (sodium carbonate, Na2CO3) can be calculated as follows:

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- (M-P) x 0.106 = concentration of Na2CO3 in % by weight

Should the (2P - M) value give a negative result there is no miễn phí alkali remaining in the cleaning solution. In this case, the cleaning effect of the solution is diminished perfectly, and more product should be immediately dosed to lớn the predetermined concentration. The table below explains the relation of the P- and M-value and corresponding concentrations of caustic-soda solution, sodium carbonate, or sodium hydrogen carbonate.

Chemical reactions:

P-Value:

NaOH + HCI > NaCI + H20

Na2CO3 + HCI > NaHCO3 + NaCI

M-Value:

NaHCO3 + HCI > NaCI + H2O + CO2

Summary:

Calculation of total alkalinity: The “total alkalinity” is only a calculation result and has no influence on cleaning effects!

The base of this calculation is the fact that NaOH is neutralized by e.g. carbonization. This carbonization neutralized some NaOH which have been present before and which have been dosed. The total alkalinity calculated back how much NaOH has been reacted by carbonization. In practice, this figure can be used for adjusting dosing pumps and to lớn identify the quantity of dosed chemicals or products to lớn reach a specific amount of “free” alkalinity which is relevant for cleaning only.

- % total alkalinity (as NaOH)

= % NaOH + (%Na2CO3 x 0.7547) + (% NaHCO3 x 0.4762)

Thank you for your time!